Method and apparatus for hardening irregular internal surfaces

ABSTRACT

Method and apparatus are disclosed for induction hardening the inside surface of Wankel engine housings. The apparatus includes a rotatable, open top support container in which an engine housing to be hardened is disposed with its axis parallel to the axis of rotation. The engine housing is disposed in the receptacle on top of an annular cam element having an inner surface contour corresponding to that of the engine. An inductor is supported adjacent the inner surface of the engine housing by means of a laterally reciprocable carriage, and the carriage also supports a cam follower assembly including a follower roller. When the support receptacle is rotated the cam follower moves along the surface of the annular cam causing the carriage to reciprocate laterally relative to the axis of rotation of the support container so that the inductor is maintained the same distance from the inner surface of the engine housing as the housing rotates. The support container is rotated by a drive assembly such that a constant scanning rate between the inductor and inner surface of the engine housing is maintained.

United States Patent 91 Budzinski METHOD AND APPARATUS FOR HARDENING IRREGULAR INTERNAL SURFACES [75] Inventor: Roger R. Budzinski, Cleveland,

Ohio

[73] Assignee: Park-Ohio Industries, Inc.,

Cleveland, Ohio 22 Filed: Oct. 16, 1972 21 Appl. No.: 297,938

[52] US. Cl 266/5 EI, 148/146, 148/150, 2l9/l0.57, 219/10.67, 266/4 R, 266/4 El,

[51] Int. Cl C2ld 1/10 [58] Field of Search 266/4 R, 4 E, 4 El, 5 R, 266/5 E, 6 R, 6 E, 6 D, 148/150, 154; 219/l0.67, 10.69, 10.71, 10.73, 10.57

[ 56] References Cited UNITED STATES PATENTS 1,957,489 5/1934 Comstock 219/124 2,828,119 3/1958 Good et al. 266/4 R 2,894,738 7/1959 Pethybridge 266/4 R X Primary Examiner-Roy Lake Assistant Examiner-Paul A. Bell Attorney, Agent. or Firm-Meyer, Tilberrv & Bodv [11'] 3,823,927 [451 July 16,1974

[5 7] ABSTRACT Method and apparatus are disclosed for induction tation. The engine housing is disposed in the receptacle on top of an annular cam element having an inner surface contour corresponding to that of the engine. An inductor is supported adjacent the inner surface of the engine housing by means of a laterally reciprocable carriage, and the carriage also supports a cam fol-' lower assembly includinga follower roller. When the support receptacle is rotated the cam follower moves along the surface of the annular cam causing the-carriage to reciprocate laterally relative to the axis of rotation of the support container so that the inductor is maintained the same distance from the inner surface of the engine housing as the housing rotates. The support container is rotated by a drive assembly such thata constant scanning rate between the inductor and inner surface of the engine housing is maintained.

9 Claims, 6 Drawing Figure s PATENImJuu s 1914 SHEET 3 OF 4 PATENTEU Jill I 51974 SHEU t (If 4 7 METHOD AND APPARATUS FOR HARDENING IRREGULAR INTERNAL SURFACES metal housing for a Wankel engine. It will be appreciated, however, that the invention is applicable to the induction heating or hardening of other forms of workpieces in which the surface to be heated or hardened has an irregular contour.

A Wankel engine'housing is annular and has an inner surface which is oval in peripheral contour. The inner surface of the housing must be hardened to provide the surface with desired wear characteristics or capabilities, and the radial depth of hardening into the body of the housing must be uniform about the periphery of the inner surface to assure uniform wear characteristics about the peripheral extent of the housing. The inner surface of the housing component can be inductively heated by scanning movement of an inductor relative to the surface, but to assure the desired uniform heating and hardening depth requires l maintaining a uniform air gap between the inductor and inner surface during the scanning movement and (2) maintaining a constant or substantially constant peripheral scanning rate.

The foregoing requirements create problems when the relative scanningmovement involves a surface having an irregular contour such as the oval contour of a Wankel engine housing. In this respect, the oval configuration of the inner surface provides regions peripherally thereof which are of different radii relative to the housing axis. Thus, a peripheral scanning speed suitable for heating a surface having a first radius of curvature will be either too slow or too fast to achieve the same degree of heating with respect to a surface area having a radius of curvature which is, respectively, less than or greater than the first radius of curvature. Further, maintaining a uniform air gap between the inductor and surface to be hardened is difficult in that a fixed reference point can not be established from which all portions of the inner surface of the engine housing are equally spaced. Therefore, relative movement between the inner surface and inductor in the direction toward and away from one another must be achieved during the scanning movement in order to maintain a uniform air gap. It will be appreciated that such relative movement of the inductor and engine housing surface toward and away from one another, togetherwith a scanning movement therebetween at a variable speed to assure a constant peripheral scanning rate, while essential to achieving the desired results, are most difficult to accomplish.

In accordance with the present invention, induction hardening of the irregular inner surface contour of an annular workpiece such as that defined by the'housing of a Wankel engine is achieved in a manner whereby the foregoing difficulties are overcome. More particularly, the present invention provides for the irregular inner surface of an annular metal workpiece to be induction hardened to a substantially constant radial depth into the body of the workpiece about the complete peripheral extent of the inner surface by providing for an inductor and the inner surface to have a relative scanning movement at a substantially constant rate, and by providing for the inductor and inner surface to be maintained in accurately spaced apart relationship during such scanning movement so that the air gap therebetween is constant.

In accordance with one aspect of the present invention, a constant air gap is maintained during relative scanning movement'between the inductor and inner surface of the engine housing by moving the inductor and housing toward or away from one another through the use of cooperable cam and cam follower assemblies therebetween which are cooperable to maintain the desired spacing. Preferably, the irregular contoured inner surface of the engine housing is rotated about a fixed axis of rotation, and the inductor is reciprocated laterally with respect to the axis of rotation through the cooperation of the cam and cam follower assemblies to maintain the desired spacing. v

In accordance with another aspect of the present invention, a uniform scanning rate between the inductor and inner surface of the housing is achieved by rotating the inner surface and the inductor relative to one another. More particularly, relative rotation is achieved by drive means which provides for the scanning movement to be at speeds which vary in accordance with the inner surface contour of the engine housing in a manner whereby the scanning rate is uniform about the periphery of the inner surface. Preferably, the annular housing is rotatedabout a fixed axis'of rotation at a variable speed which assures that relative scanning movement between the inductor and inner surface of the housing will provide a constant peripheral scanning rate about the entire periphery of the inner surface.

The engine housing can be spray quenched or flood quenched during the hardening operation and, in accordance with another aspect of the present invention,

the housing can be submerged hardened by providing for the rotating housing support to be in the form of an Another object is the provision of apparatus of the above character by which a constant air gap is maintained between an inductor and workpiece during relative scanning movement between the inner surface of the workpiece and the inductor.

Another object of the present invention is the provision of induction hardening apparatus of the above character by which a substantially constant scanning rate is maintained during relative scanning movement between the inner surface and inductor.

Yet another object of the present invention is the provision of induction hardening apparatus of the above character by which relative scanning movement between the inductor and inner surface of the workpiece is at a variable speed to assure a uniform scanning rate about the periphery of the inner surface of the workpiece.

Still another object of the present invention is the provision of induction hardening apparatus of the foregoing character by which the irregular inner surface of the workpiece and the inductor are relatively rotated and in which:

and relatively reciprocated so as to achieve a uniform scanning rate therebetween and so as to maintain a constant air gap between the inductor and inner surface during scanning movement.

A further object is the provision of induction hardening apparatus for hardening the oval shaped inner surface of an annular metal workpiece by rotating the inner surface about a fixed axis at varying speed for the surface to move relative to an inductor at a uniform scanning rate and which inductor is reciprocated radially of the fixed axis of rotation to maintain a uniform air gap between the inner surface and inductor during surface rotation.

Yet a further object of the present invention is the provision of a method of induction hardening the irregular inner surface of an annular workpiece by rotating the workpiece about a fixed axis of rotation at a variable speed and maintaining an inductor uniformly spaced from the inner surface during rotation thereof.

The foregoing objects and others, will in part be obvious and in part more fully pointed out hereinafter in conjunction with the description'of the accompanying drawings of a preferred FIG. 1 is an elevation view, partially in section,- of induction hardening apparatus;

FIG. 2 is an end elevation view of the apparatus as viewed in the direction of line 2-2 in FIG. 1;

FIG. 3 is a plan view of the apparatus of FIG. 1;

FIG. 4 is a plan view of the drive arrangement for the workpiece support taken along line 4-4 in FIG. 1;

FIG. 5 isa sectional view of the inductor of theappa: ratus taken along line 5-5 in FIG. 1; and

FIG. 6 is a diagramatic illustration of the inductor and workpiece relationship during relative scanning movement therebetween.

Referring now in greater detail to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the present invention only and not for the purpose of limiting the same, inductionheating apparatus is illustrated in FIGS. 1-4 of the drawing which includes a frame or support structure A, a workpiece support portion B mounted on frame A for rotation relative thereto, a drive mechanism Cfor imparting rotation to workpiece support portion B, and a carriage assembly D mounted on frame A for reciprocation relative thereto and to workpiece support portion B.

Frame A may be of any suitable design and structure and, in the embodiment illustrated, includes horizontally disposed channel component 10 interconnected at its opposite ends with and supported by a pair of vertical posts 14 and 16, Channel member 10 and posts 14 and 16 may be interconnected in any desired manner,

.such as bywelding, and'posts 14 and 16 may-rest on or be suitably interconnected with an underlying support surface 12 such as a floor.

Workpiece support portion. B includes an open top container or receptacle 18 having a bottom wall 20 and a peripheral side wall 22 extending upwardly therefrom. Preferably, container 18 has a peripheral contour corresponding generally to that of a workpiece to be heated although it will be appreciated that the receptacle could be otherwise contoured. Receptacle 18 is supported for rotation about a vertical axis and relative to frame A by a support shaft assembly including a embodiment of the invention shaft component 24 suitably interconnected at its upper end to a plate 25 underlying bottom wall 20 of receptacle l8. Shaft 24 extends downwardly through frame component 10 and is supported for rotation at a fixed elevation above frame component 10 by suitable bearing and support components 26 and 28 mounted respectively on frame component 10 and support surface 12. y

. Rotation is imparted to shaft 24 and thus receptacle 18 by drive portion C which includes a drive motor and gear reducer assembly 30, a drive sprocket 32, and a pair of driven sprockets 34 and 36, sprocket 34 of which is suitably mounted. on shaft 24 to impart rotation thereto. Sprocket 36 is rotatablysupported bya suitable shaft 38 mounted on support surface 12, and

sprockets 34 and 36 are interconnected by a chain component 40 which is engaged and driven bysprocket 32 of the motor and reduction gear assembly 30. It will be noted that sprockets 34 and 36 are of oval contour and are mounted on their respective shafts in 90 out-of-phase relationship relative to one another. Such a drive arrangement provides for receptacle 18 to be rotated at a variable speed each revolution thereof in response to a constant speed drive imparted to chain 40 through the motor and gear reducer assembly 30. The

purpose for this drive arrangement will be set forth more fully hereinafter.

pair of guide members52 is provided with aligned passageways adapted to receive a corresponding guide rod 54 having opposite ends attached to support posts 56. Support posts 56 are mounted on a support plate 58 which overlies frame channel 10 and is supported relative thereto by a pair of transversely extending channel components 60. Channel components 60, support plate 58, support posts 56 and guide rods 54 are fixed relative to frame assembly A. Carriage plate 50, guide members 52 and the remainder of the carriage assembly to be described are horizontally slidable relative to frame A toward and away from workpiece support portion B by movement along guide rods 54.

Carriage portion D further includes support plate 62 mounted on carriage plate 50 for reciprocating movement therewith and for pivotal movement relative thereto. More particularly, plate 62 is provided with a pair of apertured bearing blocks 64 disposed in aligned relationship adjacent opposite side edges of the support plate. Bearing blocks 64 receive the opposite ends of a rod 66 which is adjustably supported in a fixed position above carriage plate 50 by means of a pair of support arms 68 having enlarged upper ends 68a which are apertured to receive rod 66, and having threaded lower ends 68b by which the arms are secured to carriage plate 50. In this respect, the threaded lower ends of arms 68 extend through corresponding apertures in carriage plate 50 and the arms are secured to plate 50 by means of a pair of nuts 70 which threadingly engage a corresponding arm 68 and are disposed on opposite sides of plate 50. It will be appreciated that by adjusting the position of a corresponding pair of nuts 70 along an I cent the front edge of carriage plate 50 to limit pivotal movement of support plate 62 and the portion of the carriage assembly supported thereby in the counterclockwise direction as viewed in FIG. 1 of the drawing. Any suitable stop arrangement may be provided and, in the embodiment illustrated, the stop assembly is defined by a plate 76 extending across the front end of carriage plate 50 and one or more threaded bolts 78 extending upwardly from plate 76 and having a headed upper end adapted to be engaged by support plate 62 to limit movement of the corresponding end of the plate toward carriage plate 50. Plate 76 is provided with a threaded opening to receive the threaded shank of a bolt 78, and a nut 80 having threaded engagement with the bolt shank is adapted to be tightened against the upper surface of plate 76 to maintain the headed end of bolt 78 ina desired position relative to carriage plate 50.

Support plate 62 of the carriage assembly supports a housing and inductor assembly 82 which includes a housing structure 84 mounted on support plate 62 and an inductor assembly 86 supported by a wall of the housing and extending toward workpiece support portion B of the apparatus. Housing 84 may be of any suitable construction and, inthe embodiment illustrated, includes a front wall 88, a rear wall 90, a pair of side walls 92, a top wall 94 and a bottom wall 96. The several walls of the housing may be interconnected with one another in any desired manner, and bottom wall 96 is suitably interconnected with support plate 62 of the carriage assembly and, preferably, is removably interconnected therewith such as by means of nut and bolt assemblies 97. Inductor assembly 86 is mounted on front wall 88 of the housing and includes a support arm portion 98 extending forwardly and downwardly relative to wall plate 88 and having an outer end-which supports an inductor element 100 in the form of a tubular copper conductor a structure of which is described more fully hereinafter. Inductor 100 has its opposite ends connected across a suitable source of alternating current in a well known manner and, further, has its opposite ends connected to a suitable source of cooling fluid which is circulated through the inductor during an induction heating operation. The source of alternating current, not illustrated, may include a transformer which is advantageously enclosed in housing 84 and which is electrically interconnected with inductor through inductor busses 102 of support arm 98 extending therealong from the outer end of the arm and into housing 84. Support arm 98 can be mounted on housing wall 88 in any desired manner and, preferably, is removably interconnected therewith such as by nut and bolt assemblies 104.

Support plate 62 of the carriage assembly further supports a cam follower assembly 106 which includes a cam follower roller 108 supported by plate 62 through a roller support arm assembly. The roller support arm assembly includes a pair of plate components 110 extending forwardly of plate 62 from opposite sides thereof and having flange portions 112 bolted or otherwise rigidly interconnected with plate 62. The outer ends of plates 110 terminate in inturned flanges 114 which are interconnected by an insulator plate 116 which may be defined, for example, by a laminate of insulating material. The roller support arm assembly further includes a support arm 118 having a flanged upper end by which the arm is bolted or otherwise interconnec ted with plate 116. Arm 118 depends from plate 116 and is provided at its lower end with a roller carrier plate 120 which extends back toward the carriage assembly. The free end of plate 120 is provided with a notch or recess in which cam follower roller 108 is disposed, and roller 108 is supported for rotation about-a vertical axis by means of a roller pin extending therethrough and through the portions of plate 120 defining the opposite sides of the recess for the roller. The roller support arm assembly provides for roller 108.to be disposed below inductor 100 and in vertical alignment therewith for the purpose set forth more fully hereinafter.

Receptacle 18 of workpiece support assembly B is adapted to receive an annular cam component having an inner surface 132 corresponding in contour with the inner surface of the workpiece to be hardened. Roller 108 is adapted to engage and ride along inner surface 132 of cam 130 during the induction hardening process. Receptacle 18 also receives the annular workpiece W having an inner surface 134 to be induction hardened. Cam 130 is suitably supported within receptacle 18 and, preferably, is supported in spaced relationship with respect to bottom wall 20 by means of a plurality of interposed spacer elements 136. Workpiece W is disposed above and in vertical alignment with cam 130 and, preferably, is spaced therefrom by a plurality of interposed spacer elements 138. In the embodiment illustrated herein, workpiece W is the engine housing of a Wankel engine and cam 130' advantageously is defined by an identical engine housing component. These engine housing components are provided with axially extending openings therethrough which are spaced apart about the periphery of the housing component to receive bolts by which the housing component and other. portions of the engine housing are bolted together upon assembly of the engine. These openings can be used to advantage to space the cam from bottom wall 20 of the container and to space the workpiece W from the cam. In this respect, for example, spacer elements 136 and 138 can be in the form of pins having shank portions adapted to extend into the openings in the workpiece and cam components and an intermediate portion larger than the shank portion and of an axial length corresponding to the desired spacing between the cam and bottom wall 20 and between the cam and workpiece W. It will be appreciated, however, that other spacing arrangements can be employed.

In order to assure that the cam and workpiece are stably supported during operation of the apparatus, annular support components 140 and 142 are provided within receptacle 18 in surrounding relationship with respect to cam 130 and workpiece W, respectively. In a manner similar to that described hereinabove with regard to cam 130 and workpiece W, support ring 140 preferably is spaced from bottom wall 20 of receptacle 18 by a plurality of spacers 144, and support ring 142 is similarly spaced from support ring 140 by interposed spacers 146. Spacers 144 and 146 may be structurally interrelated with the support rings in the manner de-.

scribed hereinabove with regard to spacers 136 and 138. Further, it should be noted that spacers 136 and 144 can be fixedly secured to bottom wall 20 of the receptacle or removably associated therewith in any suitable manner. In any event, the spacer arrangement will be such that workpiece W and support ring 142 are readily removable from the receptacle. Preferably, cam 130 and supportring 140 are also removable from the receptacle, whereby a variety of sizes of workpieces and cams can be placed within the receptacle together with corresponding support rings to enable use of the apparatus of the induction hardening of workpieces of hardening operation both to facilitate quench hardening of inner surface 134 of the workpiece and cooling of the cam and support ring components as well as the roller and inductor 100.

Inner surface 132 of cam 130 and inner surface 134 of workpiece W are in vertical alignment and, as mentioned hereinabove, roller 108 and inductor 100 are in vertical alignment and roller- 108 is adapted to engage inner surface 132 of cam 130 during an induction heatfrom inner surface 134 of workpiece W when roller 108 engages inner surface 132 of cam 130. Leg 101 of the inductor is parallel to and slightly longer than the vertical heighth of inner surface 134 whereby the full heighth of inner surface 134 is disposed in magnetically coupled relationship with respect to inductor leg 101. Upon rotation of shaft 24 and receptacle 18, cam 130 and workpiece W rotate together about the axis of shaft 24. Since inner surfaces 132 and 134 are of irregular contour, it will be appreciatedthat rotation of cam 130 and workpiece W will cause an imaginery vertical plane tangent to inner surfaces 132 and 134 and perpendicular to the plane of the drawing in FIG. 1 to translate toward and away from the axis of shaft 24 about which the surfaces rotate. Roller 108 engages inner surface 132 of cam 130 at the point of tangency of such a plane, whereby translation in the foregoing manner and toward the axis of shaft 24 from the position illustrated in FIG. 1 causes carriage assembly D to move along ton rod 152 to move toward the opposite end of the motor, whereby piston rod 152 exerts a pull on arm 154 tending to move the carriage assembly in the direction away from the axis of shaft 24. Thus, a biasing force is applied to the carriage assembly by which roller 108' is maintained in engagement with inner surface 132 of cam 130. While the preferred biasing arrangement is that just described, it will be'appreciated that the biasing force could be otherwise provided for such as, for example, by spring means or a counterweight arranged to bias the carriage assembly away from the axis of shaft 24.

From the foregoing description it will be appreciated that the carriage assembly translates laterally relative to the axis of shaft 24 as receptacle 18, cam 130 and workpiece W rotate about the shaft axis. It will be further appreciated that continuous engagement between roller 108 and inner surface 132 of cam 130 provides for leg' 101 of inductor 100 to be maintained spaced from inner surface 134 of workpiece W by the distance X throughout each complete revolution of the workpiece about the axis of shaft 24. Thus, a constant air gap is provided between inductor leg 101 and inner surface 134 of workpiece W throughout the induction hardening operation.

In addition to maintaining a'constantair gap between the inductor and inner surface of the workpiece, the apparatus is operable to maintain a substantially constant rate of relative movement between the inductor and inner surface of the workpiece during rotation of the workpiece to achieve a uniform depth of hardening about the periphery of the workpiece. With an annular workpiece of circular configuration such a uniform scanning rate can be achieved simply by rotating the workpiece at a constant rotational speed. However, when the inner surface of the workpiece has an irregular contour constant speed rotation of the workpiece would provide for certain peripheral areas thereof to be hardened to a greater depth than other areas thereof. It is believed that this will be best understood, as will the embodiment of apparatus being described, if reference is first made to FIG. 6 of the drawing.

guide rods 54 toward the axis of shaft 24. Similarly, in I response to a translation of the imaginery plane in a direction away from'the axis of shaft 24 carriage assembly D moves along guide rods 54 away from the shaft axis. Movement of the carriage assembly in the latter direction is achieved by applying a biasing force on the carriage assembly and in a direction to bias roller 108 against inner surface 132 of cam 130. In the embodiment illustrated,'such biasing force is applied by means of a hydraulic or pneumatic motor device 150 mounted beneath fixed plate 58. Motor 150 has a piston rod 152 which in a well known manner is reciprocable in opposite directions in response to the flow of operating fluid into and out of passageways communicating with cylinder 153 on opposite sides of a piston. component therein. The outer end of piston rod 152 is interconnected with an operating arm 154 which is suitably attached to and depends from support plate of the carriage assembly.

It will beappreciated that the introduction of fluid under pressure into one end of cylinder 153 causes pis- In FIG. 6, an oval line l60'diagramatically represents the inner surface of aworkpiece to be induction hardened. Surface has a major axis 162 and a minor axis- 164 intersecting in an axis 0 corresponding to the axis of rotation about which the workpiece rotates during the induction hardening operation. Point 166 represents a point on surface 160 which is a maximum distance from axis 0, and point 168 represents a point on surface 160 which is a minimum distance from axis 0. The inductor is identified by numeral 170. It will be appreciated that if rotation of surface 160 about axis 0 is at a constant rotational speed, points 166 and 168 will rotate about the axis at the same rotational speed. It will be further appreciated, however, that point 166 will have a rate of movement, in feet perminute for example, greater than that of point 168 since it is further from axis 0 than ispoint 168. Inductor 170 of the induction heating apparatus is movable along axis 162 toward and away from axis 0 upon rotation of the workpiece in the manner described hereinabove, and it will be appreciated therefore that point 166 of surface 160 will move past inductor 170 at a greater rate of speed than will point 168. Accordingly, the depth of 160 between points 166 and 168 will be disposed at a distance from axis between the distance from the latter axis to point 168 and the distance between the axis to point 166, whereby the depth of hardening of surface 160 would vary between the points 166 and 168. Such variation in the depth of hardening is, of course, undesirable.

In accordance with the present invention, a substantially uniform depth of hardening about the periphery of inner surface 132 of workpiece W is achieved by rotating receptacle 18 and accordingly workpiece W in a manner whereby the scanning rate or rate of relative movement between the inductor and inner surface 132 of the workpiece is substantially constant. In this respect, shaft 24 is rotated at a variable rotational speed through the drive arrangement comprised of oval sprocket wheels 34 and 36 and sprocket chain 40 described hereinabove. More particularly, sprocket wheels 34 and 36 have an oval contour in which the major and minor axes of the oval are proportional to the major and minor axes of oval workpiece W. Further, sprocket wheels 34 and 36 have their major axes offset 90 relative to one another to provide for sprocket chain 40 to be retained on the wheels during rotation thereof and tomaintain chain tension. It will be appreciated of course, that sprocket wheel 36 is an idler wheel. Drive sprocket 32 is driven by motor and gear reducer assembly 30 at a constant speed of rotation, whereby sprocket 40 is driven at a constant linear speed. Sprocket wheel 34 is attached to drive shaft 24 so that the drive shaft is rotated at a variable speed which is at a minimum when the major axis of sprocket wheel 34 is in the position illustrated in FIG. 4 and at a maximum when the major axis is disposed 90 in the direction of rotation from that illustrated in FIG. 4.

As mentioned hereinabove with regard to the diagramatic illustration in FIG. 6, the point along the inner surface of the workpiece which is at the greatest distance from the axis of rotation has, for a given rotational speed, the greatest rate of movement relative to the inductor, and the. point closest to the axis of rotation has the least rate of movement relative to the inductor. Therefore, in order to provide for the rates of movement of these two points relative to the inductor to be substantially the same it is necessary to decrease the rate of movement of the Puiilt located on the major axis of the workpiece and increase the rate of movement of the point on the minor axis of the workpiece. This is achieved in accordance with the present invention by supporting workpiece W in receptacle 18 with the major axis thereof offset 90 with respect to the major axis of sprocket gear 34 on shaft 24 as illustrated diagramatically in FIG. 4. Further, leg 101 of inductor 100 is disposed in a vertical plane extending between the axes of shaft 24 and support shaft 38 of sprocket wheel 36 of the drive assembly so that the points on the major and minor axes of the workpiece are directly opposite the inductor when the workpiece is rotating at its lowest and fastest speeds, respectively. The variation in speed of rotation of the workpiece in the foregoing manner provides for inner surface 134 thereof to move past leg 101 of inductor 100 at a substantially constant rate of movement relative thereto, whereby the inner surface of the workpiece is uniformly heated and hardening to a substantially uniform depth completely about the periphery thereof can be achieved. The scanning speed compensation provided by this drive arrangement approximates a constant scanning rate within a few percent, which is adequate for hardening.

Since the inner surface of the workpiece is of irregular contour including straight and arcuate portions, the inductor will not at all times be presented normal to the surface to be hardened. Accordingly, the current carrying element or inductor is small in cross section and the magnetic field established between the inductor and workpiece, unless modified, would be quite narrow in the direction of movement of the workpiece relative to the inductor. In accordance with the present invention, however, leg 101 of inductor 100 is backed by a radiused section of magnetic material to define means for directing the magnetic flux laterally with respect to the inductor axis to increase the breadth of the magnetic field. More particularly, with reference to FIGS. 1 and 5 of the drawing a block of magnetic material 180 such as powdered iron, for example, is disposed between legs 101 and 103 of the inductor. Block 180 has a curved outer surface 182 and is provided with a recess 184 in the outer surface thereof for receiving leg 101 of the inductor. Recess 184 has a depth corresponding substantially to the diameter of the inductor leg, and block 180 is of a length corresponding substantially to the thickness of workpiece W. Further, a block of suitable insulating material 186 is disposed between block 180 and inductor leg 103 to retain block 180 in place and to insulate the block of magnetic material from leg 103. The portions of block 180 to either side of inductor leg 101 define a path by which the magnetic flux is directed laterally of the inductor leg to widen the magnetic field in the direction of movement of workpiece W to assure a desired flux density in the field between the inductor and workpiece even when a portion of the inner surface 134 of the workpiece is disposed at an angle relative to a line extending through the axis of inductor leg 101 and the axis of rotation of shaft 24. While the block of magnetic material lhas been described as being of powdered iron, it will be appreciated that other magnetic materials may be employed. For example, block 180 could be defined by laminations of magnetic material, or blocks of magnetic material other than powdered iron.

From the foregoing description, it will be appreciated that inductor is energized through a suitable source of alternating current and is translated back and forth relative to the axis of rotation of shaft 24 during rotation of receptacle 18 to achieve induction hardening of a workpiece disposed in the receptacle. Further, it will be appreciated that the receptacle is rotated at a variable speed to provide for the rate of scanning movement between the workpiece and inductor to be substantially constant whereby a uniform depth of hardening is achieved completely about the periphery of the workpiece. Preferably, the workpiece is quench hardened either by spraying quenching fluid onto the heated surface of the workpiece, providing for flooding the workpiece with quenching fluid during the heating operation, or maintaining the workpiece submerged in quenching fluid during the hardening operation. Submerged hardening of the latter character is advantageously facilitated by receptacle 18. In this respect, sidewall 22 can be provided to extend above the uppermost surface of the workpiece so that the receptacle can be filled and maintained filled with quenching fluid during the induction hardening operation. The spacing of the support components, cam and workpiece within container 18 advantageously provides for circulation of quenching fluid around and between the parts.

With reference once again to FIG. 1 of the drawing, it will be recalled that support plate 62 of the carriage assembly is pivotal relative to carriage plate 50. This pivotal movement facilitates withdrawal of the cam follower and inductor assemblies from within container 18 following an induction hardening operation to facilitate the removal of a hardened workpiece and the introduction of another workpiece to be hardened. Such pivotal movement of plate portion 62 can be achieved in any desired manner, manually or'otherwise. In accordance with another embodiment of the present invention, such pivotal movement is achieved by'means of an'extensible and retractable pneumatic or hydraulic motor 190 having one end connected to plate and its opposite end connected to plate 62. In a wellknown manner, fluid pressure can be applied to the motor cylinder 192 to displace piston rod 194 outwardly of the cylinder from the position illustrated in FIG. 1, thus to pivot plate 62 upwardly about the axis of rod 66.

' In the preferred embodiment described herein, the workpiece is rotated and the inductor is reciprocated relative thereto during-such rotation. It will be appreciated, however, that arrangements could be devised wherein the relative rotation between the workpiece and inductor and the relative reciprocation therebetween could be achieved other than in the specific manner described. For example, the inductor could be supported in a substantially fixed positiontogether with the cam follower roller and the workpiece could be rotated and the workpiece support structure and drive mechanism reciprocated as a unit to reciprocate the workpiece relative to the inductor. Other possible modifications will be apparent to those skilled in the art upon a reading and understanding of the foregoing description of the preferred embodiment. Further, while it is preferred to provide the carriage structure with a housing adapted to enclose a transformer component of the power supply, it will'be appreciated that the housing is not necessary and that the inductor support assembly could be otherwise interconnected with support plate 62 of'the carriage assembly so as to be supported thereby. Moreover, while the variable speed drive arrangement by which the workpiece is rotated at a variable speed has been defined herein as comprising a combination of oval sprocket wheels and a sprockets chain, it will be appreciated'that other drive arrangements operable in a similar manner to' rotate the workpiece at a variable speed could be employed. Still further, while the workpiece disclosed in the preferred embodiment has an oval shaped internal surface configuration, it will be appreciated that the principles of the present invention are applicable to the induction hardening of workpieces having irregular inner surfaces other than the specific contour illustrated.

As many possible embodiments of the present invention may be made and as many possible changes may be made in the embodiment herein illustrated and described, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the present invention and not as a limitation.

Having thus described my invention, I claim:

1. Apparatus for induction hardening the inner surface of an annular metal workpiece having an axis and whichinner surface is of irregular peripheral contour relative to said'axis comprising:

first support means for an annular workpiece to be hardened, an inductor, second support means for supporting said inductor within an annular workpiece on said first support means and adjacent the inner surface of said workpiece in magnetically coupled relationship with the workpiece, said inductor having opposite ends connectable across a source of alternating current, means to relatively rotate said first and second support means to produce relative scanning movement between said inductor and the inner surface of the workpiece, and means to relatively reciprocate said first and second support means generally radially with respect to said axis to maintain a predetermined air gap between said inductor and the inner surface of the workpiece during said scanning movement.

2. The apparatus of claim 1, wherein said means to relatively rotate said first and second support means includes variable speed drive means operable to provide for said scanning movement to be at a substantially constant rate. g

3. Apparatus-for induction hardening the inner surface of an annular metal workpiece having an axis and which inner surface is of irregular peripheral contour relative to said axis comprising: i

first support means for an annular workpiece to be hardened, an inductor, second support means for supporting said inductor within an annular workpiece on said first support means and adjacent-the inner surface of said workpiece in. magnetically coupled relationship with the workpiece, said inductor having opposite ends connectable across a source of alternating current, means to relatively rotate said first and second support means to produce relative scanning movement between said inductor and the inner surface of the workpiece, and means to relatively reciprocate said first and second support means generally radially with respect to said axis to maintain a predetermined air gap between said inductor and the inner surface of the workpiece during said scanning movement, said means to relatively reciprocate said first and second support means including cam and follower means including-a cam having a cam surface corresponding in contour to .the inner surface of said workpiece and follower means movable relative to said cam surface, said cam being fixed with respect to said workpiece'and said follower means being fixed with respect to said inductor.

4. The apparatus according to claim 1, wherein said inductor includes a conductor portion extending generally axially parallel with respect to said inner surface, and flux concentrating means having portions extending in the peripheral direction from opposite sides of said conductor portion.

5. The apparatus of claim 1, wherein said means to relatively rotate said first and second support means includes means to rotate said first supportmeans, and

said means to relatively reciprocate said first and second support means includes means to reciprocate said second support means, whereby said inner surface of said workpiece rotates relative to said inductor and said inductor reciprocates relative to said axis.

6. Apparatus for induction hardening the inner surface of an annular workpiece having an axis and which inner surface is of irregular peripheral contour relative to said axis comprising: first support means for a workpiece to be hardened, an inductor, second support means for supporting said inductor within an annular workpiece on said first support means and adjacent the inner surface of said workpiece in magnetically coupled relationship with the workpiece, said inductor having opposite ends connectable across a source of alternating current, means to relatively rotate said first and second support means to produce relative scanning movement between said inductor and the inner surface of the workpiece, and means to relatively reciprocate said first and second support means generally radially with respect to said axis to maintain a predetermined air gap between said inductor and the inner surface of the workpiece during said scanning movement, said means to relatively rotate said first and second support means including means to rotate said first support means, and said means to relatively reciprocate said first and second support means including means to reciprocate said second support means, whereby said inner surface of said workpiece rotates relative to said inductor and said inductor reciprocates relative to said axis, said means to reciprocate said second support means including cam and follower means comprising a cam mounted on said first support means for rotation therewith and having a cam surface corresponding in contour to the irregular inner surface of said workpiece, and a cam follower mounted on said second support means for engaging said cam surface during rotation of said first support means.

7. The apparatus of claim 6, wherein said means to rotate said first support means includes drive means for rotating said first support means at a varying rotational speed to provide for scanning of said irregular inner surface contour to be at a substantially constant peripheral rate. a

8. The apparatus of claim 7, wherein said cam is an annular component mounted on. said first support means and having an inner surface defining said cam surface, said second support means including a reciprocable platform carrying said inductor and cam follower, said cam follower engaging said cam surface during rotation of said first support means'for said cam surface to impart reciprocating movement to said platform through said follower, and means biasing said platform in the direction to maintain said cam follower in engagement with said cam surface.

9. The apparatus of claim 2, wherein said variable speed drive means includes constant speed drive motor means and variablespeed transmission means driven by said motor means. 

1. Apparatus for induction hardening the inner surface of an annular metal workpiece havinG an axis and which inner surface is of irregular peripheral contour relative to said axis comprising: first support means for an annular workpiece to be hardened, an inductor, second support means for supporting said inductor within an annular workpiece on said first support means and adjacent the inner surface of said workpiece in magnetically coupled relationship with the workpiece, said inductor having opposite ends connectable across a source of alternating current, means to relatively rotate said first and second support means to produce relative scanning movement between said inductor and the inner surface of the workpiece, and means to relatively reciprocate said first and second support means generally radially with respect to said axis to maintain a predetermined air gap between said inductor and the inner surface of the workpiece during said scanning movement.
 2. The apparatus of claim 1, wherein said means to relatively rotate said first and second support means includes variable speed drive means operable to provide for said scanning movement to be at a substantially constant rate.
 3. Apparatus for induction hardening the inner surface of an annular metal workpiece having an axis and which inner surface is of irregular peripheral contour relative to said axis comprising: first support means for an annular workpiece to be hardened, an inductor, second support means for supporting said inductor within an annular workpiece on said first support means and adjacent the inner surface of said workpiece in magnetically coupled relationship with the workpiece, said inductor having opposite ends connectable across a source of alternating current, means to relatively rotate said first and second support means to produce relative scanning movement between said inductor and the inner surface of the workpiece, and means to relatively reciprocate said first and second support means generally radially with respect to said axis to maintain a predetermined air gap between said inductor and the inner surface of the workpiece during said scanning movement, said means to relatively reciprocate said first and second support means including cam and follower means including a cam having a cam surface corresponding in contour to the inner surface of said workpiece and follower means movable relative to said cam surface, said cam being fixed with respect to said workpiece and said follower means being fixed with respect to said inductor.
 4. The apparatus according to claim 1, wherein said inductor includes a conductor portion extending generally axially parallel with respect to said inner surface, and flux concentrating means having portions extending in the peripheral direction from opposite sides of said conductor portion.
 5. The apparatus of claim 1, wherein said means to relatively rotate said first and second support means includes means to rotate said first support means, and said means to relatively reciprocate said first and second support means includes means to reciprocate said second support means, whereby said inner surface of said workpiece rotates relative to said inductor and said inductor reciprocates relative to said axis.
 6. Apparatus for induction hardening the inner surface of an annular workpiece having an axis and which inner surface is of irregular peripheral contour relative to said axis comprising: first support means for a workpiece to be hardened, an inductor, second support means for supporting said inductor within an annular workpiece on said first support means and adjacent the inner surface of said workpiece in magnetically coupled relationship with the workpiece, said inductor having opposite ends connectable across a source of alternating current, means to relatively rotate said first and second support means to produce relative scanning movement between said inductor and the inner surface of the workpiece, and means to relatively reciprocate said first and second support means generally radially with respect to said axis to maintain a predeterMined air gap between said inductor and the inner surface of the workpiece during said scanning movement, said means to relatively rotate said first and second support means including means to rotate said first support means, and said means to relatively reciprocate said first and second support means including means to reciprocate said second support means, whereby said inner surface of said workpiece rotates relative to said inductor and said inductor reciprocates relative to said axis, said means to reciprocate said second support means including cam and follower means comprising a cam mounted on said first support means for rotation therewith and having a cam surface corresponding in contour to the irregular inner surface of said workpiece, and a cam follower mounted on said second support means for engaging said cam surface during rotation of said first support means.
 7. The apparatus of claim 6, wherein said means to rotate said first support means includes drive means for rotating said first support means at a varying rotational speed to provide for scanning of said irregular inner surface contour to be at a substantially constant peripheral rate.
 8. The apparatus of claim 7, wherein said cam is an annular component mounted on said first support means and having an inner surface defining said cam surface, said second support means including a reciprocable platform carrying said inductor and cam follower, said cam follower engaging said cam surface during rotation of said first support means for said cam surface to impart reciprocating movement to said platform through said follower, and means biasing said platform in the direction to maintain said cam follower in engagement with said cam surface.
 9. The apparatus of claim 2, wherein said variable speed drive means includes constant speed drive motor means and variable speed transmission means driven by said motor means. 